Detection sensor

ABSTRACT

The invention relates to a sensor ( 1 ) comprising a pulse generator ( 2 ) and an electrode ( 3 ) connected to an output of the pulse generator ( 2 ). A detector ( 61 ) detects a change in the amplitude of the signal being present at the electrode, and a control unit ( 62 ) operatively connected to the output of the detector ( 61 ), detects the presence of a person interacting with the sensor based on the output signal of the detector ( 61 ). Furthermore, the electrode ( 3 ) is connected to the pulse generator ( 2 ) via an inductive circuit such that the sensor can detect the presence of a user but can also be used as a touch sensor. 
     In one embodiment, the pulse generator ( 2 ) via an inductive circuit is adapted to generate a pulse train with repetition rate equal to the resonance frequency of the inductive circuit or to an integer multiple of an octave of said resonance frequency. 
     An automatic faucet ( 100 ) using such sensor is further described.

TECHNICAL FIELD

The present invention relates to the field of detection sensors,particularly the field of sensors to be installed within environmentsrich in moisture or water.

The invention is preferably and advantageously applied to the field ofautomatic faucets, where the control of the water flow occurs by meansof touch or proximity sensors.

The invention is also applied to the security field, where touch andproximity sensors are installed within metal frames or conductive filmsapplied to windows, grates or gates that can be exposed to bad weather.

Particularly the invention relates to a sensor according to the preambleof claim 1 and to an automatic faucet incorporating such sensor.

PRIOR ART

Automatic faucets have become quite common for several reasons.

First of all they allow water to be saved, since when the person washinghis/her hands moves away from the faucet, this latter stops waterflowing. Secondly they are hygienic since water can be controlledwithout (or almost without) touching the faucet handles with dirtyhands.

Currently there are several types of automatic faucets, mainly based ona capacitive or infrared (IR) sensor.

The faucets with infrared sensor have the advantage that no contact withthe faucet is necessary to turn on and off the water flow, however theyhave the drawback of being uncomfortable when the basin of the sinkunderneath is desired to be filled, for example for washing clothes. Inthis case it would be necessary to remain with the hands near the sensorfor all the time necessary to fill the sink, without the possibility ofgoing away.

In order to solve this type of drawbacks, the U.S. Pat. No. 8,376,313provides a capacitive sensor for faucets that allows the water flow tobe turned on and off by a simple touch of the hand on an electrode ofthe sensor.

Although it is efficient, the solution known from U.S. Pat. No.8,376,313 however has some drawbacks, such as the need of a ground orvirtual ground connection. Moreover the U.S. Pat. No. 8,376,313 seemsnot to provide the possibility of complicated controls on the faucet,but it can only turn on or off the water flow depending on a capacitancechange detected on the sensor.

On the contrary from the U.S. Pat. No. 5,694,653 a solution of anautomatic faucet is known, that, as in the case of IR sensors, does notneed touching the faucet. This solution allows not only the turning onand off of the water flow to be controlled, but also the watertemperature to be adjusted by means of proximity sensors. However thissolution is quite complicated and cumbersome. A plurality of transmitterantennas arranged on the basin of the sink or on the faucet spout emitsan electrostatic field. A receiver antenna receives the electrostaticfield generated by the human body once it comes in contact with thetransmitted field. A processor processes the received signal forcontrolling the faucet accordingly.

OBJECTS AND SUMMARY OF THE INVENTION

It is the object of the present invention to overcome the prior artdrawbacks related to the production of detection sensors.

Particularly it is an object of the present invention to provide asensor of flexible use that can operate as a touch or proximity sensor.

These and other objects of the present invention are achieved by asensor embodying the characteristics of the annexed claims, which are anintegral part of the present description.

In one embodiment, the sensor comprises a pulse generator and anelectrode connected to an output of the pulse generator by an inductivecircuit, for example a real inductor. The sensor further comprises adetector for detecting a change in the amplitude of the signal presentat the electrode, and a control unit operatively connected to the outputof the detector and able to detect the presence of a person interactingwith the sensor depending on the output signal from the detector.

The choice of connecting the electrode to the pulse generator by aninductive circuit allows the flexibility of use of the sensor to beimproved. By changing the frequency of the generator it is possible tooperate the sensor as a touch sensor or as a proximity sensor, or as amixture of touch and proximity sensor.

This allows the sensor to be used in different applications. For examplein the case of operation as a mixed sensor, this allows the sensor to beused for controlling multi-way faucets, such as showers, which aretypically provided with at least two outlets, e.g. a spout of a faucetand a shower head.

Moreover the sensor does not need a ground or virtual ground, but it canoperate with a ground line obtained on the same PCB (printed circuitboard) where it is mounted.

In one embodiment, the sensor is provided with a pulse generator able togenerate a pulse train with a repetition rate substantially equal to theresonance frequency of the inductive circuit or to an integer multipleof an octave of such resonance frequency.

The invention further relates to an automatic faucet using such sensorand to a method for controlling automatic faucets equipped with suchsensor.

Further advantageous characteristics of the present invention will bemore clear from the description below and from the annexed claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below with reference to non-limitingexamples, provided by way of example and not as a limitation in theannexed drawings. These drawings show different aspects and embodimentsof the present invention and, where appropriate, reference numeralsshowing like structures, components, materials and/or elements indifferent figures are denoted by like reference numerals.

FIG. 1 schematically is a sensor according to the present invention;

FIG. 2 is a first variant of the sensor of FIG. 1;

FIG. 3 is a second variant of the sensor of FIG. 1;

FIG. 4 is a circuit for implementing some components of the sensor ofFIG. 1;

FIG. 5 is an automatic faucet incorporating the sensor of FIG. 1;

FIG. 6 is the change in a voltage of the sensor of FIG. 1, whenoperating as a proximity sensor, with a person interacting and notinteracting with the faucet.

FIG. 7 is a method for controlling an automatic faucet with the sensorof FIG. 1 when configured for operating as a proximity sensor.

FIG. 8 is the change in a voltage of the sensor of FIG. 1, whenoperating as a touch sensor, with a person interacting and notinteracting with the faucet.

FIG. 9 is a method for controlling an automatic faucet with the sensorof FIG. 1 when configured for operating as a touch sensor.

FIG. 10 is the change in a voltage of the sensor of FIG. 1, whenoperating as a mixed proximity and touch sensor, with a personinteracting and not interacting with the faucet.

FIG. 11 is the change in a voltage of the sensor of FIG. 1, whenoperating as a touch sensor, with a person interacting and notinteracting with the faucet.

FIG. 12 is a second method for controlling an automatic faucet with thesensor of FIG. 1, when configured for operating as a touch sensor.

FIGS. 13 and 14 are further embodiments of a sensor alternative to thoseof FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is susceptible of various modifications andalternative forms, some non-limitative embodiments, provided forexplanatory reasons, are described below in detail.

It should be understood, however, that there is no intention to limitthe invention to the specific embodiments disclosed, but, on thecontrary, the intention of the invention is to cover all modifications,alternative forms and equivalents falling within the scope of theinvention as defined in the claims.

Therefore in the description below the use of “for example”, “etc”, “or”indicate non-exclusive alternatives without limitation unless otherwisedefined; the use of “also” means “among which, but not limited to”,unless otherwise defined; the use of “including/comprising” means“including/comprising, but not limited to,” unless otherwise defined.

The term inductive circuit means a circuit having a mainly inductiveequivalent impedance; therefore such a circuit for example will be areal inductor (well-known to comprise also minimum resistive capacitivecomponents) or a real inductor with a series or parallel resistor.

FIG. 1 shows a sensor 1 intended to be installed within moistenvironments or in contact with water. In the examples below referenceis made to the application on a sink (FIG. 5) without for this reasonlimiting the scope of protection and the possible applications of thesensor.

The sensor 1 comprises a pulse generator 2 able to generate a pulsetrain with a desired frequency, selectable within an operating range ofthe pulse generator 2. In a particularly advantageous embodiment, thepulse generator is configured for generating a square wave train with arepetition rate higher than 100 KHz, and preferably higher than 300 KHz.This frequency range is particularly advantageous for the sensor appliedto automatic faucets, since it allows distinguishing one hand passingnear the faucet (therefore with the intention of controlling it) fromone hand passing far from the faucet (and therefore with no intention ofcontrolling it).

The output of the pulse generator 2 is connected to an electrode 3 by aninductive circuit 4. A resistor 5 sets the polarization of the electrode3 avoiding it remaining floating.

Downstream of the electrode, a detection and control circuit 6 detectsthe changes in the amplitude of the signal usually present at theelectrode 3, which are due to a person interacting with the electrode.Thus, therefore, the detection and control circuit detects the presenceof a person interacting with the electrode.

In the example of FIG. 1, the detection and control circuit 6 comprises:

-   -   an amplifier 60 that amplifies the signal V1 corresponding to        the one present at the electrode 3,    -   a peak detector 61 that detects the maximum amplitude of the        output signal V2 from the amplifier 60 and it provides an output        constant signal V3 dependent from the amplitude of the output of        the amplifier 60,    -   a control unit 62 receives the input constant signal V3 and it        generates an output control signal V4 that can be both a signal        necessary to control one or more devices external to the sensor,        such as one or more valves, such to control their turning on and        off, and an alarm signal intended to be interpreted and managed        by a microprocessor, external to the sensor, that in turn        controls such external devices. Due to the above, the control        unit 62 may not be provided inside the sensor and its functions        may be carried out by a processor external to the sensor itself.

In the example of FIG. 2 one alternative embodiment of the sensor ofFIG. 1 is shown. In this case, the electrode 3 is connected to theinductor 4 by a second inductor 7. When a person moves near or touchesthe electrode 3, then the signal VE present on the electrode changes andconsequently also the voltage V1 actually detected by the detection andcontrol circuit 6 changes. In this embodiment, therefore, the detectionand control circuit 6 indirectly detects a change in the voltage presentat the electrode 3.

FIG. 3 shows a further embodiment of the sensor 1, wherein othercomponents are inserted, such as a resistor 8 connected between thegenerator 2 and the inductor 4, and a Zener diode 9 that acts as ESD(Electrostatic Discharge) protection against electrostatic discharges.

Such additional components have been disclosed as possible elements thatcan be inserted within the sensor for improving its performances, evenif they are not essential for implementing the function of detecting theinteraction between the user and the electrode.

FIG. 4 shows a circuit that acts as amplifier and peak detector for thesensor; such circuit, therefore serves for implementing the functions ofthe circuit blocks 60 and 61 of FIGS. 1-3.

The circuit of FIG. 4 comprises an operational amplifier 10 whosenon-inverting input is connected to ground and whose inverting input isconnected between the resistor 11 and the resistor 12. The resistor 11is connected to the node n1 where there is provided the monitoredvoltage V1, while the resistor 12 is connected on one side to theresistor 11 and on the other side to the output of the diode 13 situatedon the output of the amplifier 10.

The RC circuit composed of the resistor 14 and of the capacitor 15 is alow-pass filter that allows an output voltage V3 to be provided that isa direct voltage with value αV1, with α (alpha) being the gain of thecircuit of FIG. 4.

Operatively, the sensor 1 is mounted on an automatic faucet such todetect the interaction between a person and the faucet.

FIG. 5 shows a sink 100 comprising a faucet 101 and a basin 102, ofwhich only a section is shown.

The faucet 101 comprises a spout 103, the water coming from two pipes104 carrying hot and cold water flows therethrough. The spout 103 of thefaucet is installed on a surface 105 by means of one or more fasteningelements. In the example of FIG. 5 the fastening element is a ring nut106 placed on the fastening surface, however, depending on the faucetmodel, it is possible for the ring nut to be placed underneath thesurface or two ring nuts to be provided, one above and one underneaththe surface 105.

In the example of FIG. 5 the faucet comprises a sensor 1 of the typeshown above with reference to FIGS. 1-4. The sensor 1, denoted by abroken line, is inserted within a recess in the surface 105 and theelectrode 3 is placed in contact with the metal spout 103 of the faucet101. Thus, the whole spout is part of the sensor and the faucet reactsto the hand 200 approaching or not the spout 103.

In order to insulate the sensor from the external environment insulatorsare provided, that is devices made of non-conductive material allowingthe faucet to be insulated from the external environment.

In the example of FIG. 5 for example an insulator 107 is provided placedbetween the fastening ring nut 106 and the surface 105 and an insulator108 is provided placed along the linkage 109 that allows the stopper 111of the sink 100 to be controlled by means of the handle 110. In oneembodiment, the insulator 108 takes the form of a plastic rubber washeror an O-ring, however other forms and solutions can be taken. If theelectrode 3 is not put in contact with the faucet spout, but it isinstalled within the spout (for example into a suitable seat) insulatedfrom the spout, then the insulators 107 and 108 may be omitted.

Anyway, it is necessary for the pipes 104 that carry hot and cold waterto be made of non-conductive material, such to guarantee the electricalinsulation from the water supplying system, it could conduct signalsthat would make the sensor less sensitive. The sensor 1 detects theinteraction of the user with the faucet, for example if the hand 200 ofa person moves near, if it touches or if it moves away from the faucet101.

As better explained with reference to the figures below, the sensor canbe configured for implementing different methods controlling the faucet,for example it can be configured such to detect only the presence of oneperson, without the need of touching it, or to detect the touch, orstill to detect both the touch and a person moving near the faucet.

The inductor 4 connecting the pulse generator to the electrode 3 is areal inductor, and as such it has also capacitive and reactivecomponents, such that the inductor acts as a mainly inductive circuit,having a gain that has maximum peaks at one resonance frequency f₀ andat frequencies distant f₀/8 (increase or decrease) of the resonancefrequency. For example if considering the inductor NL565050T-472J-PF byTDK®, it has a maximum gain at a frequency of 252 kHz and gain peaks at282.5 kHz, 315 kHz, 346.5 kHz and so on.

FIG. 6 shows the trend of the voltage V3 in the case if the pulsegenerator 2 is set for generating a pulse train with a frequency lowerthan the resonance frequency f₀ or than an octave thereof (nf₀/8 with nbeing an integer). In this case, the sensor 1 detects one handapproaching the electrode, namely it acts as a pure proximity sensor.The automatic faucet therefore can be configured for implementing themethod of FIG. 7. The control system of the faucet (for example the unit62 in FIG. 1) checks (step 701) whether the voltage V3 overcomes athreshold value sets in V_(thp) such that V_(rest)<=V_(thp). If thevoltage is lower than the threshold value (preferably selected higherthan V3 _(rest) such to consider possible noises), then this means thatthere is no interaction between a person and the faucet and the methodreturns to step 701. When (time t₀ of FIG. 6) a person moves near theelectrode (or the spout of the faucet if the electrode is connectedthereto), then the voltage V3 increases by passing from the rest valueV3 _(rest) to the detection value V3 _(prox)>V_(thp); therefore thecontrol system checks that the measured voltage is higher than thethreshold value and it turns the faucet on (step 702).

Then the control system starts to check (step 703) whether the measuredvoltage has dropped below the threshold value, that is whetherV3<V_(thp). If not, then the check is repeated, otherwise it means thatthe interaction with the faucet has ended (time t₁), for example becausethe user brings his/her hands far away from the faucet, then the voltageV3 goes back to the rest value V3 _(rest). Now, the control system turnsthe faucet off (step 704) and the algorithm of the control systemreturns to step 701, waiting for turning again the faucet on.

FIG. 8 shows the trend of voltage V3 in the case if the pulse generator2 is set to generate a pulse train with a frequency higher than theresonance frequency f₀ or than an octave thereof (nf₀/8 with n being aninteger). In this case, the sensor 1 detects the touch of one hand withthe faucet, namely it acts as a pure touch sensor. Therefore theautomatic faucet can be set for implementing the method of FIG. 9. Thecontrol system of the faucet (for example unit 62 of FIG. 1) checks(step 901) whether the faucet is turned on, for example by controlling aflag in a memory field. If the faucet is turned off, then the controlsystem checks (step 902) whether the voltage V3 goes below a thresholdvalue sets in V_(tht) such that Vrest<=V_(tht). If the voltage is higherthan the threshold value, then it means that there is no interactionbetween a person and the faucet and the method returns to step 902. When(time t₀ of FIG. 8) a person touches the electrode (or the faucet spoutif the electrode is connected thereto) by the hand, then the voltage V3decreases by passing from the rest value V3 _(rest) to the detectionvalue V3 _(touch)<V_(tht); therefore the control system checks whetherthe measured voltage is lower than the threshold one, which correspondsthe faucet being touched. In order to check whether the touch isintentional, and not accidental, (for example because one desires toclean the faucet), the control system is set for waiting for apredetermined quite short time Δt, for example 1 or 2 seconds (step 903)and then it repeats the check on the voltage value (step 904). If evenin this case the voltage is lower than the threshold one, then thecontrol system checks that the electrode has been intentionally touchedand it turns the faucet on (step 905).

Then, when the person removes the hand from the contact with theelectrode (time t₁ of FIG. 8), the voltage V3 rises above the thresholdV_(tht) and it returns to the initial value V3 _(rest). This is checkedby the control system that, after turning the faucet on, and afterwaiting for a time Δt2 (e.g. 5 seconds) (step 906), it checks (step 907)whether the measured voltage has risen above the threshold value, namelyif V3>V_(tht). If yes, it means that there are no irregular situations,such as an unintentional extended contact of the hand with the faucet ora contact with an object that brings the electrode to ground; thealgorithm therefore returns to step 901. If not, an operating abnormalcondition is verified and the control system turns the faucet off (step908).

When the faucet is turned on, in the example of FIG. 9 the water issupplied up to a time t2, when a new touch of the electrode by the userhas occurred. This event is checked at step 909, where the controlsystem checks whether there is a new contact with the electrode, that isif V3<=V_(tht), in this case it turns the faucet off (step 908).

As an alternative, the control system can be configured such to supplywater for a predetermined time, in this case the step 909 describedabove can be replaced by a timer, when it expires the faucet is turnedoff (step 909).

On the contrary the example of FIG. 10 shows the trend of the voltage V3if the pulse generator 2 is set for generating a pulse train with afrequency equal to the resonance frequency f₀ or of an octave thereof(nf₀/8 with n being an integer). In this case, the sensor 1 detects boththe proximity and the contact of one hand with the electrode, namely itacts as a mixed proximity and touch sensor.

Such as shown in FIG. 10, when the hand approaches the electrode, thenthe voltage V3 rises above the rest value V_(rest) maintained inconditions of absence of an interaction between a person and theelectrode. Therefore the behavior is similar to what explained withreference to FIG. 6. When a person touches with his/her hand theelectrode, then the voltage V3 drops below V_(rest), as mentioned abovewith reference to FIG. 8.

In this case, the control system 62 can be configured such to takedifferent decisions depending on the fact that one hand touches or onlymoves near the electrode.

For example in a multi-way faucet, the control system may turn on andoff the water flow of one way when the hand moves near or away from theelectrode, and on the contrary it may turn on and off the water flow ofanother way when the hand touches the contact. In a faucet for a shower,this for example would allow the water flow of the shower to be turnedon when the person goes near the sensor, and the water flow to bedeviated from the shower head to the hand-held shower head when theelectrode is touched.

In the light of the above, it is clear how the described sensor is ableto achieve the suggested objects, and to allow, depending on itsconfiguration, a proximity and a touch condition, or both of them, to bedetected.

Therefore it is clear that the person skilled in the art can makedifferent changes to the sensors and to the methods for controllingautomatic faucets described above, without for this reason departingfrom the scope of protection of the present patent, such as defined inthe annexed claims.

For example it is clear that several components described above asdiscrete components can be integrated or that different functionalblocks of the circuit can be implemented by an integrated circuit or aprogrammable logic (PLC).

As regards the threshold values V_(tht) and V_(thp), they can beprearranged or can be defined after a calibration step after which thevalue of the voltage V3 is checked with a person in the conditioninteracting or not interacting with the faucet. Therefore the thresholdvoltage can be selected between two values of the voltage V3 measuredduring the calibration step, particularly, ΔV3 being the differencebetween the measured signals, the threshold voltage is selected as equalto the voltage under non-interaction conditions (V3 _(rest)) plus orminus (depending it is V_(thp) or V_(tht) respectively) 30-35% of ΔV3.Therefore this calibration step allows an optimal threshold voltage tobe selected that considers possible manufacturing tolerances of thesensor components.

In a further advantageous embodiment, the system uses a mobile thresholdin order to distinguish between a condition of interaction and acondition of non-interaction with the faucet.

Depending on the configuration with which the sensor is installed in thefaucet, for example whether the electrode is connected to the faucetspout or not, and depending on the salt level of the water flowingthrough the faucet, the voltage V3 used by the control system to decidehow controlling the faucet, in absence of an interaction, mayconsiderably be different in case the faucet is turned on or off, namelyin presence of water flowing or not through the faucet spout.

The use of a mobile threshold allows a good ability of the sensor to bekept for distinguishing between a user interacting or not interactingwith the sensor with the faucet in the turned on or off conditions.

In the example of FIG. 11 a sensor 1 is considered configured foroperating as a pure touch sensor.

With reference to FIG. 11, at time zero the faucet is turned off andthere is no interaction between the faucet and the physical person,therefore the voltage V3 is at the rest value V3 _(rc). The thresholdvoltage V_(tht), in this initial step is set at the value V_(tht) 0, forexample determined after a calibration step as described above.

At time to the voltage V3 drops below the threshold value V_(tht), setin V_(tht) 0, going to V3 _(touch). Such as described with reference tothe method of FIG. 12, the system controlling the faucet detects that atouch has occurred (step 1001), it checks that the faucet is turned off(step 1002) and it turns it on (step 1003).

Now (time t0), the threshold voltage is set to zero V_(tht) (step 1004)and the control system waits for detecting a new touch (step 1001).

At the following clock moments, the control system calculates again thevalue of the threshold voltage keeping it always below the signal valueV3.

In one embodiment the threshold voltage is calculated as:V _(tht) =V3*0.65

Since the threshold is always kept below the value of the signal V3, thefaucet control method can be simplified with respect to the example ofFIG. 9.

When at time t1 the touch between the hand of a person and the sensorends, the voltage V3 increases to value V3 ro, lower than V3 rc due tothe water passing through the faucet, however the threshold remainsbelow the value of V3, therefore the sensor control system does notcarry out any actions on the faucet.

When at time t2 the sensor detects a new touch, the sensor controlsystem checks that a touch has occurred and that the faucet is turnedon, therefore it turns it off (step 1005) and it goes back to a standbycondition waiting for a new touch (step 1001).

Even if referred to a sensor configured to operate as a touch sensor,the example of FIGS. 11 and 12 however is not limitative and the use ofthe mobile threshold may be made, with suitable precautions, also forsensors configured as proximity sensors or mixed proximity and touchsensors. For example, when the sensor has to operate as a proximitysensor, the mobile threshold will be kept higher than the signal V3(e.g. V_(th)=V3*1.35) and not lower as described for the example ofFIGS. 11 and 12.

In the case of sensors operating as mixed sensors, therefore with thepulse generator set for generating a pulse train with a repetition rateequal to the resonance frequency or to a multiple of an octave of suchfrequency, two mobile thresholds are used: a mobile threshold is keptlower than the signal V3, the other one higher than such signal. Bymonitoring when the signal V3 crosses one threshold or the other one, itis possible to decide how to control valves, devices or appliances(electric or hydraulic ones).

In one embodiment, the control unit 62 detects not only the change inthe voltage of the electrode, but it measures also a differentialintensity vector between the signal and a threshold (a mobile thresholdor not depending on the configurations). In this embodiment thereforethe sensor is able to generate an output V4 variable as a function ofsuch differential intensity vector. Since such differential intensityvector depends (in case of a proximity detection) on the distance of oneperson from the sensor, this allows the flexibility of use of the sensorto be further enhanced, it may be configured for controlling the flowrate, the mixing temperature or the selection of the supply depending onthe distance of the person from the sensor. For example the sensor maybe set to increase the water flow rate when the hand of a person movesnear the sensor and to reduce it when the hand moves away therefrom.

In one embodiment that uses the differential intensity vector, theelectrode of the sensor is made as a metal plate with a triangular shapeas shown in FIG. 13. Therefore the electrode has a detection surface 300that increases as moving towards x. By touching (or moving near to) theelectrode in different positions, there is a different area ofinteraction between the electrode and the finger, and consequently, thedifferential intensity vector is different. For example is consideringFIG. 13, the area of interaction of the finger at position x1 is smallerthan the one at position x2. Therefore this solution allows a kind ofsliding contact (slider) to be made, therefore by moving the finger(touching or not) along the electrode in the direction x, the sensordetects a continuous change in the differential intensity vector, whichwill be increasing or decreasing depending on the direction of movement.Therefore the control unit 62 is configured for controlling a device oran appliance downstream of the sensor depending on the change of thedifferential intensity vector, for example for increasing the flow rateor the temperature of a water flow in a faucet depending on the movementof the finger along the electrode.

As an alternative to a shape offering variable detection surfaces, suchas shown in FIG. 13, in the example of FIG. 14, the electrode 3 iscomposed of several separated detection areas, denoted by the references301, 302, 303 and 304. By touching one or more of the areas 301-304 thedifferential intensity vector changes, and therefore the sensor cancontrol in a different manner a device or an appliance downstream of thesensor, for example, presuming that the sensor is configured foroperating as a touch sensor, if the areas 301 and 302 are touched thewater flow rate is adjusted, if areas 303 and 304 are touched the watertemperature is adjusted. In this embodiment, therefore, the sensor hasan electrode with different detection surfaces and it is configured forcontrolling a device in a manner depending on the interaction of oneperson with one or more of said detection areas.

It has to be noted that, although the several embodiments have beendisclosed above with reference to the application in the field ofautomatic faucets, the sensor described above may be applied in manyother fields, such as for example the field of user interfaces or thesecurity field, therefore the sensor can control electric appliances,such as alarms or signal transmitters, or it can be used for detectingthe interaction of a person with an area of a device.

The invention claimed is:
 1. An automatic faucet comprising a metalspout and a detection sensor, wherein the detection sensor comprises: apulse generator, an electrode connected at one end to an output of thepulse generator via an inductive circuit and to the metal spout at theother end, a detector adapted to detect a change in the amplitude of thesignal being present at the electrode, and a control unit operativelyconnected to the output of the detector and adapted to detect thepresence of a person interacting with the sensor based on the detectoroutput signal.
 2. The faucet of claim 1, further comprising a valve andwherein the control unit is configured to generate an output controlsignal to control the valve.
 3. The faucet of claim 1, wherein the pulsegenerator is adapted to generate a pulse train with repetition rateequal to the resonance frequency of the inductive circuit or to aninteger multiple of an octave of said resonance frequency.
 4. The faucetof claim 1, wherein the control unit is adapted to compare the detectoroutput signal with a threshold signal and to output a control signaldepending on such a comparison.
 5. The faucet of claim 4, wherein thecontrol unit is configured to automatically change in time the thresholdsignal, and in particular it is configured to keep said threshold signalalways below or always above the detector output signal.
 6. The faucetof claim 5, wherein the pulse generator is adapted to generate a pulsetrain with a repetition rate substantially equal to the resonancefrequency of the inductive circuit or to an integer multiple of anoctave of said resonance frequency, and wherein the control unit isconfigured to compare the detector output signal with two thresholdsignals variable in time, a first one of said two threshold signalsbeing kept always below the detector output, and a second one of saidtwo threshold signals being kept always above the detector output. 7.The faucet of claim 6, wherein the control unit is adapted to determinean initial value of the threshold signal based on a calibration phasewherein the value of the detector output voltage is detected in bothcondition of interaction and non-interaction of a person with thesensor.
 8. The faucet of claim 5, wherein the control unit is adapted todetermine an initial value of the threshold signal based on acalibration phase wherein the value of the detector output voltage isdetected in both condition of interaction and non-interaction of aperson with the sensor.
 9. The faucet of claim 5, wherein the controlunit is adapted to determine an initial value of the threshold signalbased on a calibration phase wherein the value of the detector outputvoltage is detected in both condition of interaction and non-interactionof a person with the sensor.
 10. The faucet of claim 1, wherein theelectrode has an interaction surface which increases along a maindirection, and wherein the control unit is adapted to generate a controlsignal which depends on the movement of a finger along said maindirection.
 11. The faucet of claim 1, wherein the electrode has aplurality of interaction surfaces separated from each other, and whereinthe control unit is adapted to generate a control signal which dependson the interaction surface or surfaces with which a person interacts.